Furnace equipment



Patented Mar. 28, 1933 UNITEDHSTATES PATENT orrlcs WILLIAM A. DARRAH, orCHICAGO, ILLINOIS FURNACE EQUIPIVIENT Application filed January 7, 1929,Serial 330,870. Renewed. August 12, 1932.

This invention relates to equipment and methods for constructingfurnaces and other combustion devices. It is particularly applicable tofurnaces used for'heating air or other gases in the class of equipmentknown as heaters or air heaters. My invention, however, may be aplied tomany other purposes such as the construction of furnacesft'or heatingsteel, ceramic material, etc, or for baking, drying and other purposes.

Some of the objects of this invention are to provide economical, simpleand efficient.

means for constructing combustion devices, which will be durable,efficient and relatively inexpensive. Another object of this inventionis to provide means for reducing the depreciation of combustion chamberswhich has hitherto been relatively high. My invention also makes itrelatively easy to repair or rebuild combustion devices in part on thesectional principle instead of making it necessary to rebuild the entirestructure. Other objects of this invention will be apparent from thespecification, claims and drawings.

In order to illustrate my invention most effcotively I have shown; oneform of structure in accordance with my principles applied to a furnacefor heating air or air heater. It will of course be understood'that theprinciples and features of construction illustrated here may be appliedin many other ways to other devices without departing from the scope ofthis invention.

My invention is designed to provide equipment which permits readyexpansion of component parts when subjected to relatively highdifferences of temperature.

Referring to the drawings: i Figure 1 shows a front elevation of oneform of air heater constructed in accordance with my invention,

Figure 2 shows diagrammatically a side elevation of the same air heater,while Figure 3 shows a plan view of my device;

Figure 4 shows in perspective a detail of chamber 11 and is preferably'located'near one of the expansion blocks as illustrated i Figures 1, 2and 8,

Figure 5 shows in perspective a detail of a slightly modified form whichalso comes within the scopeof-my invention,

Figure 6 shows a portion of a combustion chamber constructed 1naccordance with my invention but slightly modified from the ar- Vrangement shown in Figure 3.

The equipment consists of a shell or housing 1 which may be constructedof steel, brick or other building material as desired. I prefer applyinsulation as shown by 2, 3 and 4. The insulation may be any of the wellknown materials such as magnesium carbonate, .infusorial earth andsimilar materials. The housing may be reinforced by structural steel,buck stays, 5, 6, 7, 8, 9 and ldas shown.- A combustion chamberpreferably constructed of highly refractory material. such as siliconcarbide is indicated by 11. The floor of air heater 1 may be constructedof ordinary fire brick or concrete as indicated by 12 and in a'similarmanner the floor of the combustion chambermay be constructed offirebrick or othermedium graderefractory 13 and preferably covered inthe hotter portion with a layer of'sand or other comminuted refractory14. Inorder to provide means for maintaining the lower portion ofcombustion chamber 13 cool, I provide a series of airports 1 5, 16 and17, arranged in a. manner to'be'described subsequently. The combustionchamberll is preferably constructed with vertical walls 18 and 19 and acovering. in the form of a tile or arch 20.

The combustion chamber 11 is surmounted by a secondary combustionchamber 21 which in most cases may be constructed from fire,

restrict the flow of products of combustion from the. combustion laterto be described. t I Aburner 26 arranged for'oil, gas, powdered coal,etc., is placed at one 'end of combustion chamber for reasons the floor14 of the combustion chamber;

An opening or air entering port 27 is provided in one portion of theheater housing and an air leaving port 2 8 is provided at an-' otherportion of the heater housing. I A movable by-pass damper 29 connectingto operating handle is provided within the heater housing in such alocation that by moving said damper 29 variable portions of the air'which enters through port 27 may be bypassed directly to port 28, thebalance being caused to circulate around the outside Walls of combustionchamber 11, thereby heating the air or circulating gases and partiallycooling the combustion chamber walls.

In operating a device of this kind, the walls of combustion chamber 11particularly walls 18 and 19 and to an appreciable extent walls 22 and23 become intensely heated. Manyrefractory materials which willwithstand high temperatures are subject to considerable expansion underheat and some refracto-riesare itis constructed, it is highly desirableto provide a system of expansion joints throughout the structure.

It is not sufiicient in the case of even relatively. small cevices toprovide for expansion joints at each end, as even in this case growth orexpansion will take place within the interior of various walls, causingwarping, cracking and destruction of the "material.

To overcome this diificulty, I have provlded a series of column tile 31,one form of which is shown in perspective in Figure 4 and an alternativeone in Figure 5. The socalled column tile are named for the reason thatthey are used to form a relatively permanent column or pier whichcarries a considerable portion of the load of the structure and retainthe side walls in position without restricting other expansion. Thecolumn tile 31, therefore are provided with grooves or re-entrantcorners 32, 33 arranged to engage with corresponding corners .34 and 35of wall tiles 36, 37 etc. At the end of the combustion chamber I mayprovide a vertical wall 38 carryingcolumn tile 39 and 40 at its corners,where the combustion chamber 11 connects with the front wall 41 of theheater and also provide expansion joints indicated by 42 and 43 similarin construction to joints provided at39and40. m

In order to prevent walls 18 and 19 from spreading I provide a series ofstretchers ortile as for example 44 and 45 which serve to hold walls 18and 19 from moving outward.

Arch 20 of course serves to hold the walls from moving inward as well asthe fact that they are interlocked with foundation 13 as shown. Furtherarch 20 is provided with a series of expansion joints 46,47 and 48 whichif desired may be covered with brick or tile 49, 50 and 51.

. Referring to Figure 5 column tile 52 is provided with two openings orgrooves 53 and 54 which serve to retain the wall tile in position in thesame manner as in the cases of column tile 31. In the case of columntile 52 the ends of the wall may be cut at 90 instead of on a bevel asin the case of column tile 31. V

Column tile 31 may beplaced with the extending portion either in the airspace'as shown in Figure 3 or inthe combustion chamber as shown inFigure 4. Further the stretcher tile 44 and 45 may be placed with Itheir greatest width horizontal asshown in Figure 3 or arranged asindicated by56, 57 and 58 with their greatest dimension vertical.Stretcher tile 44 and 45 may be supported in any manner as for exampleat one end b a brick-59 corbeled out from the wallof the air chamber andatfthc other end by a brick 60 corbeled out from the combustion chamber.wall. I find it convenient to provide a dovetail or interlockingarrangement as shown by 61 in Figure 4 permitting the individual columntile to be locked one to the other, thus preventing lateral orhorizontal displacement. I

Inoperating a device constructed in ac- ;ordance with my invention, fuelis delivered into combustion chamber 11 from burner 26 and the greaterportion of the combustion orv dinarily takes place in the lower partbefore the productsof combustion enter the secondary chamber 21. Thisarrangement insures that "the combustible materialwill be completelyburned producing no soot or dirt, the distance of travel through thecombustion chamber the greatest section of the com bustionv chamber bothserving tocontrol the time that the combustible materials remain in thehot zone. It will be of course understood that combustion of the moredifficult portions of the fuel substantially stops as soon as thetemperature to which the fuel is subjected falls below a definite value.I

In actual operation air heaters of this kind are frequently operatedunder such .condi-.

tions that the air pressure within the heater is lower than the pressureof the atmosphere outside. Such a condition would result in a tendencyto draw the products of combustion out of the combustion chamber too rap.idly and before combustion has'b-een completed. The retarding wall 25serves to overcome this difliculty by restricting the opening fromcombustion chamber 21. The layer of sand or'comminuted material 14 onthe lower portion of combustion chamber 11 serves to provide a readilyexpandable protection to the floor of combustion chamber 11, thus makingit unnecessary to provide elaborate expansion means in this portion ofthe device. Further the cooling ducts 15, 16 and 17 serve to cause theflow of air beneath the floor of combustion chamber 11, thus furtherreducing the temperature of the floor. This arrangement is ofconsiderable importance especially in'those cases in vhich the heatermay be constructed on a wooden or concrete floor. IVithout means oftlie'kind described, the floor would be charred and the concretedisintegrated, thus not only causing a serious heat loss, but resultingin a failure of the structure.

It will be apparent that equipment of the kind described, when in thehands of the average plant operator, will be rapidly raised from a verylow ten'iperature up to a. maximum temperature frequently exceeding 2000F. within a period of fifteen to thirty minutes. Such a change intemperature causes the strains and expansion previously mentioned and isone of the reasons for the necessity of the type of structure heredisclosed.

In the device which I have invented the major portion of the load of thestructure is carried on the column tile as shown, the

wall tile normally carrying a relatively slightload or in some casesmerely their own weight. Under these conditions, each wall tile is freeto expand as required independently of the balance of the structure. Byallowing each portion of the structure'to expand independently of theassembly the tendency for warping, cracking and other defects arelargely overcome. v

It will, of course, be understoodthat a structure in accordance with myinvention may be constructed, using silicon carbide, aluminum oxide,chrome oxide, magnesite and other refractories, although I have foundthat silicon carbide is well suited for this work and the structureshown is particularly adapted for this material.

In addition to providing great mechanical flexibility the device which Ihave shown provides a high degree of thermal. flexibility in that a widevariation may take place in the volume of fuel burned in the combustionchamber without seriously affecting thefpe'rformance of the equipment.The device is also quite flexible from the standpoint of handling air orother gases in that, the air which is being heated may be caused to passaround the combustion chambers in the space provided, therefore, orabove the combustion chamber, or the air may be by-passed directly fromthe entering port 27 to the leavin port 28, the adjustment useddepending of course upon the volumes of air or gases being heated,desired temperatures, greatest sectional area available or other obviousfactors. The

use, however, of by-pass damper 29 or the equivalent is of considerableimportance in the commercial operation of this equipment.

Itis not always easy to obtain absolutely clean combustion so that nosoot or dirt re- Inasmuch mains in the combustion gases. as thisequipment is frequently employed in connection with drying, baking orheating materials which are light in color and which must not bediscolored,'absolutely clean combustion is essential. Cleanliness ofcombustion is obtained only when all conditions are correct. Somefactorsare of more importance than others, however, and one important point isto maintain a high and uniform temperature within the combustionchamber. I have found that it is not satisfactory to maintain a hightemperature only at the dis charge end of the combustion chamber. I

have even found that a high temperature at ble for clean combustion areobtained when steps are taken to insure that the portion of thecombustion chamber around the burner i sintensely hot. This result maybe obtained by constructing the walls of the combustion chamber at thispoint from material which has the characteristics of greatrefractoriness combined with a poorer heat conductivity than the balanceof the combustion chamber.

"In other words, I may use such refractories as aluminum oxide, silicaconipounds, sillinianite, mullite, etc., for that portion of thecombustion chamber adjacent to the burner and extending along the flamefor an appreciable distance. I may also obtain the same result byconstructing a semi-insulating wall out- 'side the combustion chamber asshown by reference numbers 70, 71 and 72 in Figure 3. Other obviousexpedients may be employed such as restricting the flow of air or othergases being heated, so that they do not re;

move as much h-eatfrom that portion ofthe combustion chamber adjacent tothe burner as they do from other portions. For example air or othergases to be heated ordinarily would enter in portion 74 and travelsubstantially horizontally through passages .75,

76, 77 and 78. 7 Some of the air or gases being ieated may by-passthrough adj ustable'opening 79and leave by exit port 80. Other of thecirculating gases being heated will travel;

upward through openings 81, 82, 83, 84, 85,

lid

etc., thus serving to partially cool the walls 36, 37, etc. Obviouslythe size of the openings between the supporting tiles such as 44preferably arranged to coincide so that the combustion chamber is ineffect constructed from a series of short lengths. This is notabsolutely essential however. It is quite advantageous to arrange sothat arch 20 is carried primarily on column tile 31 or the equivalentinstead of upon the intermediate portions of the wall, although theparticular details of construction depend to some extent upon theobvious features of design.

I have found that the arrangement of the burner materially below centerline of the V combustion chamber is of decided advantage in obtaining arelatively uniform heat distribution throughout the combustion chamber.It will be obvious that the hot products of combustion being lighterthanair tend to rise and by placing the burner initially appreciably belowthe center line, the rising tendency of the products of combustion ispartially compensated for.

It should be understood that many obvious modifications may be made inthe arrangement, dimensions and structure described and shown herewithout departing from the scope of my invention. Various materials maybe substituted for those specifically mentioned and many modificationsmay be made in the shapes and proportions in the average parts of theequipment. 7

Having now fully described my invention, what I claim as new and wish tosecure by Letters Patent in the United States, is as follows:

1. A gas heaterconsisting of a housing, a combustion chamber ofrefractory material located therein, a passage for gas being heatedalong said combustion chamber, a fuel supply device delivering fuel tosaid combustion chamber, said combustion chamber beingcon structed witha series of column members and a series of intermediate panel members,said panel members being arranged to eX- pandindependently of eachother, and a restricted'opening in said combustion chamber connecting toa space outside said combustion chamber and within said housin 2. Aheater consisting of a housing, a combustion chamber therein, passagesfor the material being heatedaround said combustion chamber, ports insaid combustion chamber connecting the latter to the interior of saidhousing and'means for'controlling the in sucha manner that the heatconductivity of the portionof said combustion chamber adjacent said fuelsupply device is higher thanthe heat conductivity of the balance of saidcombustion chamber.

4. A combustion chamber consisting of a series of supporting columns anarchcarried by said columns and a series of independently eXpansiblepanel units between said columns forming a substantially air tightcontinuous wall for said combustion chamber.

5. A combustion chamber constructed of highly refractory materialarranged in a series of independently expansible units, a floor for saidcombustion chamber formed of comminuted material, a fuel supply devicefor said combustion chamber arranged to deliver fuel and air at a pointappreciably below the middle portion of said combustion chamber.

6, In a heater for gases, a burner for sup-' plying fuel to the interiorof said combustion chamber, a refractory combustion chamber constructedfrom a series of independently expansible refractory units joinedtogether to prevent appreciable leakage, and a series of supports formaintaining said individual units in permanent alignment,

7. A combustion chamber consisting of a series of independentlyexpansible units interlocked to prevent appreciable leakage andconstructed from highly refractory materials, a fuel supply devicetherefor, said combustion chamber'being arranged to permit lesser heatflow from the portions an appreciable distance away from the fuel supplydevice than from the portions adjacent said fuel supply device.

8. The process of burning fuel which consistsin delivering said fuel toone end of a closed highly refractory combustion cham-.

ber, restricting the outflow of combustion gases from said combustionchamber, and re stricting the flow of heat fromthe portion of saidcombustion chamber away from the fuel supply device. i

' 9. A gas heater consisting of a housing, a combustion chamber withinsaid housing, an inlet in said housing for said gas being heated, anoutlet in said housing for said gas,

a duct for said gas in contact with said com- 10. A gas heaterconsisting of a housing, a-I

combustion chamber within said housing, an

inlet in said housing for said gas being heated, an outlet in saidhousing for said gas, a duct for said gas 1n said housing in contactwith said combustlon chamber and a by-pass duct for said gas in saidhousing between said inlet and said outlet and means to control therelative flow of said gas in said ducts.

11. A gas heater consisting of a housing, a combustion chamber withinsaid housing, an inlet in said housing for said gas being heated, anoutlet in said housing for said gas,

a duct in housing for said gas in contact.

with said combustion chamber and a by-pass duct located in said housingfor said gas and connecting said inlet and said outlet and means tocontrol the relative flow of said gas in said first mentioned duct andsaid by-pass duct.

12. In a gas heater a combustion chamber, a housing enclosing saidchamber, a duct in said housing directing a portion of the flow of gasbeing heated in contact with saidcombustion chamber and another duct insaid housing bypassing said directing duct and means to control therelative flow of gas in said duct system.

13. A multiple passage combustion chamber consisting of a series ofrelatively thick columns retaining a series of relatively thinintermediate panels arranged for independent expansion, a cover for saidcombustion chamber constructed in sections to permit individualexpansion of each section, and a burner for supplying fuel into saidcombustion chamber, near one end, and a restricted outlet near the otherend.

14. A gas heater consisting of a housing, a

combustion chamber therein constructed. of

refractory material and arranged in inde pendently expansiblelongitudinal sections, independent bracing members for said unitsextending from said housing to each of said independent sections, and apassage for gas being heated about said combustion chamber and incontact therewith.

15. In a gas heater a combustion chamber constructed of a series ofindependently eX- pansible units of highly refractory material, a burnerfor delivering fuel into said combustion chamber, a passage beneath saidcombustion chamber for removing heat there from, and a restricted outletfrom said combustion chamber into the space around said combustionchamber and arranged so as to maintain a higher pressure in saidcombustion chamber than in said surrounding space.

16. In a gas heater a combustion chamber constructed of independentlyexpansible units of silicon carbide, a burner for delivering fuel intosaid combustion chamber, a passage below said combustion chamber forcooling the lower portion therein and a restricted outlet from saidcombustion chamber into the space around said chamber and arranged so asto maintain a higher pressure in said chamber than in said space.

17. A gas heater consisting of a housing, a combustion chamber withinsaid housing constructed of independently expansible units interlocked,one to the other, in a'manner to prevent appreciable leakage into or outof said combustion chamber, a burner arranged to deliver fuel into saidcombustion chamber, bracing members from said housing to said combustionchamber and ducts for removing heated gases from said combustionchamber. s

18. A device for heating gases consisting of a housing, a combustionchamber therein and spaced from'said housing for a portion of itssurface, said combustion chamber being formed of independentlyeXpansib-le refractoryunits, independent, laterally extending supportsfor said units of said combustion chamber, and a passage for gases beingheated adjacent said combustion chamber and within said housing, and arestricted port connecting said chamber with said housing.

19. A combustion chamber consisting of a series of independentlyexpansible refractory units interlocked to prevent leakage, a gaspassage outside of and adjacent said combustion chamber, a. fuel supplydevice near one end of said combustion chamber, and'an upper passage for"products of combustion above said combustion chamber and communicatingwith it, and a restricted opening near the end of said upper pasasgeconnecting said combustion chamber with said gas passage, saidrestricted opening having a lesser area than the cross section of saidcombustion chamber and arranged to maintain a greater pressure Withinsaid chamber than outside same.

20. A combustion chamber consisting of two substantially horizontalpassages arranged one above the other, said passages being constructedof independently expansible units interlocked together to preventleakage, a duct outside said combustion chamber, a fuel supply devicenear one end of said combustion chamber and a restricted opening throughthe Walls of the upper portion of said combustion chamber near the endand communicating with said passages, said restrict ed opening beingless in area than the cross section of said combustion chamber, therebymaintaining a higher pressure in said combustion chamber than in saidpassages.

21. In a combustion chamber a Wall of refractory material having onesidesubstantially unbroken and composed of a series of columns supportingintermediate panels, a

housing and arranged to bypass said direct ing duct.

23. A gas heater consisting of a housing, a combustion chamber in saidhousing, ducts in said housing beneath and above said com bustionchamber, and a bypass duct in said housing, arranged todirect acontrolled portion of gases to be heated away from contact with saidcombustion chamber.

24. A gas heater consisting of a housing, a combustion chamber in saidhousing, an inletiand an outlet to said housing, a duct along saidcombustion chamber in contact With the sides thereof, a duct connectingsaid inlet and outlet directly, and means for controlling the relativevolume of gases passing alongside said combustion chamber and therelative volume of gas passing directly from said inlet to said outlet.

25. In a gas heater a combustion chamber, a burner for delivering fuelinto said combustion chamber, a ductbeside said combustion'chamber forcooling a portion thereof, an inlet to said housing, an outlet to saidhous- I ing and means for proportioning the amount of gas being heatedwhich cools said combustion chamber and the amount Which passes directlyfrom said inlet to said outlet.

WILLIAM A. DARRAH.

